Since its discovery, fluorine has been known as an aggressive element. It is especially aggressive with organic compounds, such as hydrocarbons. Many scientists have shown interest in the development of techniques for direct fluorination of polymeric materials. This can be done by using a mixture of fluorine and a carrier-diluting fluid which reduces the aggressiveness of the fluorine. In the prior art, helium, He, and argon, Ar, have been used as the carrier fluid, but in commercial fluorination, nitrogen, N.sub.2, is the standard carrier fluid because of its lower cost. Representative prior art patents which disclose fluorination processes and the carrier fluids used include: U.S. Pat. No. 2,811,468 to Joffre; U.S. Pat. Nos. 3,674,432, 3,711,595, and 3,775,489 to Professor Margrave et. al.; U.S. Pat. Nos. 3,998,180 and 4,081,574 to Hawkins et. al.; and U.S. Pat. No. 4,576,837 to Tarancon. He, Ar, and N.sub.2 all reduce the aggressiveness of the fluorine, induce some solubility of the byproduct hydrogen fluoride HF and help carry the heat to some degree to and from the polymer. As ideal gases, they have low density (1 atm and 350K), they induce low dipole moment, and they have a low critical temperature. These three factors in these gases minimize their heat capacity per unit of volume and their solubility of the byproduct HF. Any HF which is not dissolved by the gas remains on the surface of the polymer and blocks the continuation of the fluorination reaction. The result is a decrease in the efficiency of the fluorination process.
It is therefore an object of the present invention to provide an improved carrier fluid for use in fluorination of polymeric materials, wherein the carrier fluid has a high critical temperature, a high induced dipole moment, a high density, a high heat capacity, a high solubility for hydrogen fluoride, decreases the preheating time, maintains the reaction temperature at a more uniform level, increases the rate of fluorination, and which is inexpensive and safe to use.